Science and Technology I · Textbook solutions

Lenses

Every solved example, exercise, and miscellaneous question — in the order the textbook teaches them. · 14 questions

Exercise

14 q
  1. Ex Q1
    Match the columns in the following table and explain them.
    Column 1Column 2Column 3
    FarsightednessNearby object can be seen clearlyBifocal lens
    PresbyopiaFar away object can be seen clearlyConcave lens
    NearsightednessProblem of old ageConvex lens
  2. Ex Q2
    Draw a figure explaining various terms related to a lens.
  3. Ex Q3
    At which position will you keep an object in front of a convex lens so as to get a real image of the same size as the object ? Draw a figure.
  4. Give scientific reasons:
    Ex Q4(a)
    Simple microscope is used for watch repairs.
  5. Ex Q4(b)
    One can sense colours only in bright light.
  6. Ex Q4(c)
    We can not clearly see an object kept at a distance less than 25 cm from the eye.
  7. Ex Q5
    Explain the working of an astronomical telescope using refraction of light.
  8. Distinguish between:
    Ex Q6(a)
    Farsightedness and Nearsightedness
  9. Ex Q6(b)
    Concave lens and Convex Lens
  10. Ex Q7
    What is the function of iris and the muscles connected to the lens in human eye?
  11. Solve the following examples.
    Ex Q8(i)
    Doctor has prescribed a lens having power +1.5 D+1.5\ \text{D}. What will be the focal length of the lens? What is the type of the lens and what must be the defect of vision?
  12. Ex Q8(ii)
    5 cm5\ \text{cm} high object is placed at a distance of 25 cm25\ \text{cm} from a converging lens of focal length of 10 cm10\ \text{cm}. Determine the position, size and type of the image.
  13. Ex Q8(iii)
    Three lenses having power 22, 2.52.5 and 1.7 D1.7\ \text{D} are kept touching in a row. What is the total power of the lens combination?
  14. Ex Q8(iv)
    An object kept 60 cm60\ \text{cm} from a lens gives a virtual image 20 cm20\ \text{cm} in front of the lens. What is the focal length of the lens? Is it a converging lens or diverging lens?